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Inverse-designed metastructures that solve equations

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Science  22 Mar 2019:
Vol. 363, Issue 6433, pp. 1333-1338
DOI: 10.1126/science.aaw2498

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Solving equations with waves

Signal processing of light waves can be used to represent certain mathematical functions and to perform computational tasks on signals or images in an analog fashion. Such processing typically requires complex systems of bulk optical elements such as lenses, filters, and mirrors. Mohammadi Estakhri et al. demonstrate that specially designed nanophotonic structures can take input waveforms encoded as complex mathematical functions, manipulate them, and provide an output that is the integral of the functions. The results, demonstrated for microwaves, provide a route to develop chip-based analog optical computers and computing elements.

Science, this issue p. 1333

Abstract

Metastructures hold the potential to bring a new twist to the field of spatial-domain optical analog computing: migrating from free-space and bulky systems into conceptually wavelength-sized elements. We introduce a metamaterial platform capable of solving integral equations using monochromatic electromagnetic fields. For an arbitrary wave as the input function to an equation associated with a prescribed integral operator, the solution of such an equation is generated as a complex-valued output electromagnetic field. Our approach is experimentally demonstrated at microwave frequencies through solving a generic integral equation and using a set of waveguides as the input and output to the designed metastructures. By exploiting subwavelength-scale light-matter interactions in a metamaterial platform, our wave-based, material-based analog computer may provide a route to achieve chip-scale, fast, and integrable computing elements.

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